UA-145931898-1

The Different Types of Threaded Inserts
All threaded inserts are designed with female threading to support the use of a fastener with male threading, but there are several different types of threaded inserts, each of which features a unique design. Helical threaded inserts, for example, are characterized by a coiled design, typically consisting of steel or bronze. The respective metal is coiled up in the precise size and shape to support the threaded fastener.

http://www.ctri-eng.com/threading-inserts/